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  <div class="section" id="module-repr">
<span id="repr-alternate-repr-implementation"></span><h1>8.19. <a class="reference internal" href="#module-repr" title="repr: Alternate repr() implementation with size limits."><tt class="xref py py-mod docutils literal"><span class="pre">repr</span></tt></a> &#8212; Alternate <a class="reference internal" href="#module-repr" title="repr: Alternate repr() implementation with size limits."><tt class="xref py py-func docutils literal"><span class="pre">repr()</span></tt></a> implementation<a class="headerlink" href="#module-repr" title="Permalink to this headline">¶</a></h1>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">The <a class="reference internal" href="#module-repr" title="repr: Alternate repr() implementation with size limits."><tt class="xref py py-mod docutils literal"><span class="pre">repr</span></tt></a> module has been renamed to <tt class="xref py py-mod docutils literal"><span class="pre">reprlib</span></tt> in Python 3.  The
<a class="reference internal" href="../glossary.html#term-to3"><em class="xref std std-term">2to3</em></a> tool will automatically adapt imports when converting your
sources to Python 3.</p>
</div>
<p><strong>Source code:</strong> <a class="reference external" href="http://hg.python.org/cpython/file/2.7/Lib/repr.py">Lib/repr.py</a></p>
<hr class="docutils" />
<p>The <a class="reference internal" href="#module-repr" title="repr: Alternate repr() implementation with size limits."><tt class="xref py py-mod docutils literal"><span class="pre">repr</span></tt></a> module provides a means for producing object representations
with limits on the size of the resulting strings. This is used in the Python
debugger and may be useful in other contexts as well.</p>
<p>This module provides a class, an instance, and a function:</p>
<dl class="class">
<dt id="repr.Repr">
<em class="property">class </em><tt class="descclassname">repr.</tt><tt class="descname">Repr</tt><a class="headerlink" href="#repr.Repr" title="Permalink to this definition">¶</a></dt>
<dd><p>Class which provides formatting services useful in implementing functions
similar to the built-in <a class="reference internal" href="functions.html#func-repr"><em>repr()</em></a>; size limits for different
object types are added to avoid the generation of representations which are
excessively long.</p>
</dd></dl>

<dl class="data">
<dt id="repr.aRepr">
<tt class="descclassname">repr.</tt><tt class="descname">aRepr</tt><a class="headerlink" href="#repr.aRepr" title="Permalink to this definition">¶</a></dt>
<dd><p>This is an instance of <a class="reference internal" href="#repr.Repr" title="repr.Repr"><tt class="xref py py-class docutils literal"><span class="pre">Repr</span></tt></a> which is used to provide the <a class="reference internal" href="#repr.repr" title="repr.repr"><tt class="xref py py-func docutils literal"><span class="pre">repr()</span></tt></a>
function described below.  Changing the attributes of this object will affect
the size limits used by <a class="reference internal" href="#repr.repr" title="repr.repr"><tt class="xref py py-func docutils literal"><span class="pre">repr()</span></tt></a> and the Python debugger.</p>
</dd></dl>

<dl class="function">
<dt id="repr.repr">
<tt class="descclassname">repr.</tt><tt class="descname">repr</tt><big>(</big><em>obj</em><big>)</big><a class="headerlink" href="#repr.repr" title="Permalink to this definition">¶</a></dt>
<dd><p>This is the <a class="reference internal" href="#repr.Repr.repr" title="repr.Repr.repr"><tt class="xref py py-meth docutils literal"><span class="pre">repr()</span></tt></a> method of <tt class="docutils literal"><span class="pre">aRepr</span></tt>.  It returns a string
similar to that returned by the built-in function of the same name, but with
limits on most sizes.</p>
</dd></dl>

<div class="section" id="repr-objects">
<span id="id1"></span><h2>8.19.1. Repr Objects<a class="headerlink" href="#repr-objects" title="Permalink to this headline">¶</a></h2>
<p><a class="reference internal" href="#repr.Repr" title="repr.Repr"><tt class="xref py py-class docutils literal"><span class="pre">Repr</span></tt></a> instances provide several attributes which can be used to provide
size limits for the representations of different object types,  and methods
which format specific object types.</p>
<dl class="attribute">
<dt id="repr.Repr.maxlevel">
<tt class="descclassname">Repr.</tt><tt class="descname">maxlevel</tt><a class="headerlink" href="#repr.Repr.maxlevel" title="Permalink to this definition">¶</a></dt>
<dd><p>Depth limit on the creation of recursive representations.  The default is <tt class="docutils literal"><span class="pre">6</span></tt>.</p>
</dd></dl>

<dl class="attribute">
<dt id="repr.Repr.maxdict">
<tt class="descclassname">Repr.</tt><tt class="descname">maxdict</tt><a class="headerlink" href="#repr.Repr.maxdict" title="Permalink to this definition">¶</a></dt>
<dt id="repr.Repr.maxlist">
<tt class="descclassname">Repr.</tt><tt class="descname">maxlist</tt><a class="headerlink" href="#repr.Repr.maxlist" title="Permalink to this definition">¶</a></dt>
<dt id="repr.Repr.maxtuple">
<tt class="descclassname">Repr.</tt><tt class="descname">maxtuple</tt><a class="headerlink" href="#repr.Repr.maxtuple" title="Permalink to this definition">¶</a></dt>
<dt id="repr.Repr.maxset">
<tt class="descclassname">Repr.</tt><tt class="descname">maxset</tt><a class="headerlink" href="#repr.Repr.maxset" title="Permalink to this definition">¶</a></dt>
<dt id="repr.Repr.maxfrozenset">
<tt class="descclassname">Repr.</tt><tt class="descname">maxfrozenset</tt><a class="headerlink" href="#repr.Repr.maxfrozenset" title="Permalink to this definition">¶</a></dt>
<dt id="repr.Repr.maxdeque">
<tt class="descclassname">Repr.</tt><tt class="descname">maxdeque</tt><a class="headerlink" href="#repr.Repr.maxdeque" title="Permalink to this definition">¶</a></dt>
<dt id="repr.Repr.maxarray">
<tt class="descclassname">Repr.</tt><tt class="descname">maxarray</tt><a class="headerlink" href="#repr.Repr.maxarray" title="Permalink to this definition">¶</a></dt>
<dd><p>Limits on the number of entries represented for the named object type.  The
default is <tt class="docutils literal"><span class="pre">4</span></tt> for <a class="reference internal" href="#repr.Repr.maxdict" title="repr.Repr.maxdict"><tt class="xref py py-attr docutils literal"><span class="pre">maxdict</span></tt></a>, <tt class="docutils literal"><span class="pre">5</span></tt> for <a class="reference internal" href="#repr.Repr.maxarray" title="repr.Repr.maxarray"><tt class="xref py py-attr docutils literal"><span class="pre">maxarray</span></tt></a>, and  <tt class="docutils literal"><span class="pre">6</span></tt> for
the others.</p>
<p class="versionadded">
<span class="versionmodified">New in version 2.4: </span><a class="reference internal" href="#repr.Repr.maxset" title="repr.Repr.maxset"><tt class="xref py py-attr docutils literal"><span class="pre">maxset</span></tt></a>, <a class="reference internal" href="#repr.Repr.maxfrozenset" title="repr.Repr.maxfrozenset"><tt class="xref py py-attr docutils literal"><span class="pre">maxfrozenset</span></tt></a>, and <a class="reference internal" href="stdtypes.html#set" title="set"><tt class="xref py py-attr docutils literal"><span class="pre">set</span></tt></a>.</p>
</dd></dl>

<dl class="attribute">
<dt id="repr.Repr.maxlong">
<tt class="descclassname">Repr.</tt><tt class="descname">maxlong</tt><a class="headerlink" href="#repr.Repr.maxlong" title="Permalink to this definition">¶</a></dt>
<dd><p>Maximum number of characters in the representation for a long integer.  Digits
are dropped from the middle.  The default is <tt class="docutils literal"><span class="pre">40</span></tt>.</p>
</dd></dl>

<dl class="attribute">
<dt id="repr.Repr.maxstring">
<tt class="descclassname">Repr.</tt><tt class="descname">maxstring</tt><a class="headerlink" href="#repr.Repr.maxstring" title="Permalink to this definition">¶</a></dt>
<dd><p>Limit on the number of characters in the representation of the string.  Note
that the &#8220;normal&#8221; representation of the string is used as the character source:
if escape sequences are needed in the representation, these may be mangled when
the representation is shortened.  The default is <tt class="docutils literal"><span class="pre">30</span></tt>.</p>
</dd></dl>

<dl class="attribute">
<dt id="repr.Repr.maxother">
<tt class="descclassname">Repr.</tt><tt class="descname">maxother</tt><a class="headerlink" href="#repr.Repr.maxother" title="Permalink to this definition">¶</a></dt>
<dd><p>This limit is used to control the size of object types for which no specific
formatting method is available on the <a class="reference internal" href="#repr.Repr" title="repr.Repr"><tt class="xref py py-class docutils literal"><span class="pre">Repr</span></tt></a> object. It is applied in a
similar manner as <a class="reference internal" href="#repr.Repr.maxstring" title="repr.Repr.maxstring"><tt class="xref py py-attr docutils literal"><span class="pre">maxstring</span></tt></a>.  The default is <tt class="docutils literal"><span class="pre">20</span></tt>.</p>
</dd></dl>

<dl class="method">
<dt id="repr.Repr.repr">
<tt class="descclassname">Repr.</tt><tt class="descname">repr</tt><big>(</big><em>obj</em><big>)</big><a class="headerlink" href="#repr.Repr.repr" title="Permalink to this definition">¶</a></dt>
<dd><p>The equivalent to the built-in <a class="reference internal" href="functions.html#func-repr"><em>repr()</em></a> that uses the
formatting imposed by the instance.</p>
</dd></dl>

<dl class="method">
<dt id="repr.Repr.repr1">
<tt class="descclassname">Repr.</tt><tt class="descname">repr1</tt><big>(</big><em>obj</em>, <em>level</em><big>)</big><a class="headerlink" href="#repr.Repr.repr1" title="Permalink to this definition">¶</a></dt>
<dd><p>Recursive implementation used by <a class="reference internal" href="#repr.Repr.repr" title="repr.Repr.repr"><tt class="xref py py-meth docutils literal"><span class="pre">repr()</span></tt></a>.  This uses the type of <em>obj</em> to
determine which formatting method to call, passing it <em>obj</em> and <em>level</em>.  The
type-specific methods should call <a class="reference internal" href="#repr.Repr.repr1" title="repr.Repr.repr1"><tt class="xref py py-meth docutils literal"><span class="pre">repr1()</span></tt></a> to perform recursive formatting,
with <tt class="docutils literal"><span class="pre">level</span> <span class="pre">-</span> <span class="pre">1</span></tt> for the value of <em>level</em> in the recursive  call.</p>
</dd></dl>

<dl class="method">
<dt>
<tt class="descclassname">Repr.</tt><tt class="descname">repr_TYPE</tt><big>(</big><em>obj</em>, <em>level</em><big>)</big></dt>
<dd><p>Formatting methods for specific types are implemented as methods with a name
based on the type name.  In the method name, <strong>TYPE</strong> is replaced by
<tt class="docutils literal"><span class="pre">string.join(string.split(type(obj).__name__,</span> <span class="pre">'_'))</span></tt>. Dispatch to these
methods is handled by <tt class="xref py py-meth docutils literal"><span class="pre">repr1()</span></tt>. Type-specific methods which need to
recursively format a value should call <tt class="docutils literal"><span class="pre">self.repr1(subobj,</span> <span class="pre">level</span> <span class="pre">-</span> <span class="pre">1)</span></tt>.</p>
</dd></dl>

</div>
<div class="section" id="subclassing-repr-objects">
<span id="subclassing-reprs"></span><h2>8.19.2. Subclassing Repr Objects<a class="headerlink" href="#subclassing-repr-objects" title="Permalink to this headline">¶</a></h2>
<p>The use of dynamic dispatching by <a class="reference internal" href="#repr.Repr.repr1" title="repr.Repr.repr1"><tt class="xref py py-meth docutils literal"><span class="pre">Repr.repr1()</span></tt></a> allows subclasses of
<a class="reference internal" href="#repr.Repr" title="repr.Repr"><tt class="xref py py-class docutils literal"><span class="pre">Repr</span></tt></a> to add support for additional built-in object types or to modify
the handling of types already supported. This example shows how special support
for file objects could be added:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">repr</span> <span class="kn">as</span> <span class="nn">reprlib</span>
<span class="kn">import</span> <span class="nn">sys</span>

<span class="k">class</span> <span class="nc">MyRepr</span><span class="p">(</span><span class="n">reprlib</span><span class="o">.</span><span class="n">Repr</span><span class="p">):</span>
    <span class="k">def</span> <span class="nf">repr_file</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">obj</span><span class="p">,</span> <span class="n">level</span><span class="p">):</span>
        <span class="k">if</span> <span class="n">obj</span><span class="o">.</span><span class="n">name</span> <span class="ow">in</span> <span class="p">[</span><span class="s">&#39;&lt;stdin&gt;&#39;</span><span class="p">,</span> <span class="s">&#39;&lt;stdout&gt;&#39;</span><span class="p">,</span> <span class="s">&#39;&lt;stderr&gt;&#39;</span><span class="p">]:</span>
            <span class="k">return</span> <span class="n">obj</span><span class="o">.</span><span class="n">name</span>
        <span class="k">else</span><span class="p">:</span>
            <span class="k">return</span> <span class="nb">repr</span><span class="p">(</span><span class="n">obj</span><span class="p">)</span>

<span class="n">aRepr</span> <span class="o">=</span> <span class="n">MyRepr</span><span class="p">()</span>
<span class="k">print</span> <span class="n">aRepr</span><span class="o">.</span><span class="n">repr</span><span class="p">(</span><span class="n">sys</span><span class="o">.</span><span class="n">stdin</span><span class="p">)</span>          <span class="c"># prints &#39;&lt;stdin&gt;&#39;</span>
</pre></div>
</div>
</div>
</div>


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  <ul>
<li><a class="reference internal" href="#">8.19. <tt class="docutils literal"><span class="pre">repr</span></tt> &#8212; Alternate <tt class="docutils literal"><span class="pre">repr()</span></tt> implementation</a><ul>
<li><a class="reference internal" href="#repr-objects">8.19.1. Repr Objects</a></li>
<li><a class="reference internal" href="#subclassing-repr-objects">8.19.2. Subclassing Repr Objects</a></li>
</ul>
</li>
</ul>

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